Problem: $ { {3} \times \left[\begin{array}{rrr}{3} & {4} & {-1} \\ {-1} & {1} & {-2}\end{array}\right] = {?} } $
Answer: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rrr}{3}\times{3} & {3}\times{4} & {3}\times{-1} \\ {3}\times{-1} & {3}\times{1} & {3}\times{-2}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{9} & {12} & {-3} \\ {-3} & {3} & {-6}\end{array}\right]}$